[R-gui] general design questions

On Mon, Aug 18, 2008 at 6:56 AM, Antje <niederlein-rstat at yahoo.de 
<mailto:niederlein-rstat at yahoo.de>> wrote:

    Hello,

    I try to develop a GUI with gWidgets (TclTk) but I guess my little
    application already starts to be messy...

    First question: How shall I handle updates of widgets triggered by
    event handling? So far, I simply took the widget-object I want to
    update as a global variable but that's not a good style. Any
    suggestions how to handle this?


It's possible to specify a "user" object when registering the callbacks, 
I think. The "user data" is then passed as the last parameter to the 
handler. Another good way to control the scoping is nesting environments 
(e.g. through closures). That is, your object does not need to be global 
(in the workspace) but it can be in a parent environment. In fact, 
global variables won't even work when you put your code into a 
namespaced pacakge, because the namespace will be locked.

    Second question: What are my possibilities to stay flexible? For
    example: I though it makes sense to use a gpanedgroup for a
    checkboxgroup with variable number of items (to make it scrollable
    if it's getting too large). But this does not work like I thought
    and the items simply disappear at the end of the panel.


I don't think the paned group is what you want here. Split paned widgets 
are to allow the user to control the allocation of space in a GUI, 
usually in either the horizontal or vertical directions. If you're GUI 
is growing too large, you'll need to make it so that only a portion of 
the GUI is visible at once. One way to do that is with scrolled windows. 
See the use.scrollwindow parameter for ggroup().

 


    Third question: How to structure the GUI? Builing, Sizing, Arraging,
    filling with content (not every object has some initial content).
    For example, I realized that I have to set the svalue for the
    gpanedgroup after adding the objects.


Well this is an art and depends on your GUI. Split panes are difficult 
in that they require one to specify a numeric value for the split 
position. This is a similar problem to specifying the initial size of a 
window. 

The simplest way is just to guess a good initial position. This 
is usually not too bad. Adjusting the split automatically might not be a 
good idea, since it should be under the control of the user.

 


    I don't know, but I have the impression to create my GUI quite
    unstructured and I'm afraid to loose overview soon...

    The small examples for the usage of different components are very
    useful but I'm looking for some hints on how to create a more
    complex application (what to do when and how).

    Thanks a lot for every tip!

    Antje

On Tue, Aug 19, 2008 at 1:38 AM, Antje <niederlein-rstat at yahoo.de 
<mailto:niederlein-rstat at yahoo.de>> wrote:

    Hi Michael,

    thanks a lot for your answer.



        On Mon, Aug 18, 2008 at 6:56 AM, Antje
        <niederlein-rstat at yahoo.de <mailto:niederlein-rstat at yahoo.de>
        <mailto:niederlein-rstat at yahoo.de
        <mailto:niederlein-rstat at yahoo.de>>> wrote:

           Hello,

           I try to develop a GUI with gWidgets (TclTk) but I guess my
        little
           application already starts to be messy...

           First question: How shall I handle updates of widgets
        triggered by
           event handling? So far, I simply took the widget-object I want to
           update as a global variable but that's not a good style. Any
           suggestions how to handle this?


        It's possible to specify a "user" object when registering the
        callbacks, I think. The "user data" is then passed as the last
        parameter to the handler. Another good way to control the
        scoping is nesting environments (e.g. through closures). That
        is, your object does not need to be global (in the workspace)
        but it can be in a parent environment. In fact, global variables
        won't even work when you put your code into a namespaced
        pacakge, because the namespace will be locked.


    Can you give me a simple example, please? I'm not sure if I
    understand correctly how this can work. (Or maybe there is already
    some kind of documentation I can check for these possibilities...)


There's documentation and examples in the help for addHandler. It's the 
"action" parameter.

 



           Second question: What are my possibilities to stay flexible? For
           example: I though it makes sense to use a gpanedgroup for a
           checkboxgroup with variable number of items (to make it
        scrollable
           if it's getting too large). But this does not work like I thought
           and the items simply disappear at the end of the panel.


        I don't think the paned group is what you want here. Split paned
        widgets are to allow the user to control the allocation of space
        in a GUI, usually in either the horizontal or vertical
        directions. If you're GUI is growing too large, you'll need to
        make it so that only a portion of the GUI is visible at once.
        One way to do that is with scrolled windows. See the
        use.scrollwindow parameter for ggroup().


    Oh, thanks a lot. I was not aware of the scrolling opportunity if
    the ggroup.


         

           Third question: How to structure the GUI? Builing, Sizing,
        Arraging,
           filling with content (not every object has some initial content).
           For example, I realized that I have to set the svalue for the
           gpanedgroup after adding the objects.


        Well this is an art and depends on your GUI. Split panes are
        difficult in that they require one to specify a numeric value
        for the split position. This is a similar problem to specifying
        the initial size of a window.


    Is there anything I can do beside, setting a fixed size with pixel
    values?
    For example if I'd like to initially maximze the window... (I know
    that it's possible with TclTk).


I am not that familiar with tcl/tk but in general UI toolkits require 
you specify pixels for positions of things like that. If it's not so 
important for the user to be able to adjust the layout, why not just 
skip the paned widget? They're rarely very helpful.

 


        The simplest way is just to guess a good initial position. This
        is usually not too bad. Adjusting the split automatically might
        not be a good idea, since it should be under the control of the
        user.


    Of course, I just set it initially.

    Ciao,
    Antje


         

           I don't know, but I have the impression to create my GUI quite
           unstructured and I'm afraid to loose overview soon...

           The small examples for the usage of different components are very
           useful but I'm looking for some hints on how to create a more
           complex application (what to do when and how).

           Thanks a lot for every tip!

           Antje